Of course, as I was probably around 9, I don't think I knew the word amputate yet, so this might be a little revisionist.
BUT - the truth is - that is NOT an amputator. It is actually the most important device a mohel could own. It is called a shield - in Hebrew, a "Magen" (מגן), and it's goal is to shield all the parts we don't want to cut from being nicked or otherwise by the scalpel/blade we use to excise the foreskin.
The parts we don't want to cut include the glans, the scrotum, the baby's belly, not to mention the sandak's hands.
When a traditional bris milah is performed, the foreskin is grabbed and drawn foreward, and this shield is applied in such a manner that the only thing on the outside is the foreskin, while below it is everything else. The mohel simply cuts along the shield, and the circumcision is complete.
The best way to know exactly where to apply that shield, because once foreskin is being drawn forward all the skin looks the same and can result in an uneven cut, or a taking off too much or too little cut, is to draw a line on the foreskin following the circumference of the highest point of the glans all around.
Once the line is drawn and the foreskin is drawn forward correctly, a simple (and correct) application of the shield along the surgical line will result in a beautiful circumcision, and a baby who is otherwise protected from anything beyond our stated goal of removing the foreskin.
Please note the Magen above is not to be confused with this device - called the MOGEN Clamp. I do not own a Mogen Clamp (more about clamps here) and I do not recommend its use. There are mohels who use it - hopefully with good care and with positive results. But Google "Mogen Clamp" before you allow any mohel to use it on your son.
For fun - more pictures of magen shields. Note the differences in style, width of slit and whether there is a groove in the slit. And, of course, any ornamental components, such as gold, silver, or with engraving. :